Why do we need to
know the number of persons with different kinds of disabilities?
And, why are the results of different surveys in the same
population so different?

Doing a survey is simple - go to different
homes, ask if they have any disabled persons and fill the
information in a form.

Let us take a
look at some data. WHO suggests that 10% of a population may
have a disability. Yet if you look at country reports, the
percentage of disabled persons in a population may vary from
0.5% to 17%. Less developed countries and poor communities
seem to report less persons with disabilities compared to
developed countries.

Often
different surveys conducted in the same country, give very
different results. Why is that?

This course
attempts to take a look at some of the reasons behind such
data.